To reproduce:
add an AnchorPane
add a Button to the AP
invoke "Replace to with i18n string" for Text property
invoke "Reset to default"
press on gearbox to show menu again -- property is still waiting for variable name i.e. value is not default one that is just a text.
It's also ambiguously if it's ok that user is impossible to replace text value with i18n string when multi-lines mode enabled